A security/surveillance system is field that has been studied for a long period of time and security surveillance technology includes a security camera scheme, an infrared (IR) scheme, an ultrasound scheme, an acoustic measuring scheme, and the like.
Korean Patent Publication Application Laid-Open No. 2003-0005105 (Security Apparatus and Control Method Thereof) discloses a method that may monitor a surveillance space and provide countermeasures while a user is out through a detection means using a general IR sensor, an internal photographing camera, a speaker that generates an alert sound, and a high performance microphone for recording detected sound. That is, the above disclosure relates to an apparatus that may install a security system in a predetermined surveillance space to be monitored, and thereby detect an intrusion using an IR sensor and generate an alert sound, and may also transfer internal image and acoustic information to a security company, a police station, and a preset telephone to thereby monitor a security state, and a method of controlling the apparatus.
The above method may not detect an intrusion when an intruder is outside the intrusion detection range of an IR sensor, or when the intruder uses a method that enables the body temperature of the intruder not to be detected. The detectable range of the IR sensor is very narrow and thus, a large number of systems as above need to be installed for the thorough security. However, the malfunction of sensors occurring due to various external changes has become an issue.
As another related art, the U.S. Pat. No. 5,828,626 (Acoustic Object Detection System and Method, Otincon Corporation) discloses a method that emits an audible sound wave within a surveillance space, measures intensity of a normal wave acoustic signal and a phase change depending on whether an object is present, and thereby outputs an alert sound. However, instead of measuring a acoustic transfer function, the above method simply measures only intensity of an acoustic signal and thereby alerts an intrusion based on the difference. Therefore, a malfunction occurs due to a change in an acoustic signal by an environmental change and peripheral noise.
As still another related art, the U.S. Pat. No. 7,535,351 (Acoustic Intrusion Detection System) discloses a technology that generates an acoustic sound of an audio frequency domain using a dipole speaker (emitter), locates a pair of microphones (detectors) in dipole acoustic offset positions (null), and compares magnitude of a sound wave and a phase occurring due to an intruder with magnitude of a sound wave and a phase before intrusion to thereby detect the intrusion. However, the above method is limitedly used for a specified security area and malfunction usually occurs due to an environmental change or peripheral noise.
As yet another related art, Korean Patent Publication No. 2009-0123752 (Security System and Method Using Measurement of Sound field variation) discloses a security system and method that determines whether an intrusion has occurred in a predetermined space using a difference between an initially set sound and a sound by the intrusion. The above method erroneously recognizes, as the intrusion, a variation of a acoustic transfer function occurring due to a change in temperature of air and convection change, and a change in a temporal characteristic of a speaker, a microphone, and the like. Alternatively, since cameras for secondary verification are installed to be distributed and thereby used, it is inconvenient to install, move or remove the cameras.
A security camera scheme that is a conventional security/surveillance method needs to consecutively photograph a moving picture during security surveillance, and to store a large capacity of image information. Therefore, a price becomes expensive and power consumption becomes an issue in the case of a consecutive operation. To verify a security situation in real time, a human being needs to continuously monitor a camera image or to monitor a security situation such as intrusion through processing of smart image information. In this case, a very high cost is required and there are many constraints due to lack of concentration of a human being, inaccuracy of an intrusion recognizing algorithm, and the like. Even though an IR security module is inexpensive and uses a small amount of power, a non-operation/malfunctioning issue of security/surveillance is present when an intrusion occurs in such a manner that a subject wears IR blocking clothes or uses an IR blocking apparatus, and the intrusion detection range is narrow. An ultrasound security module has a power issue due to low efficiency of sound wave transfer to an air layer and also has a difficulty in applying a scan scheme due to high straightness. In most security monitoring modules, an area for detecting an intrusion or a security situation is significantly limited and narrow due to fundamental constraints thereof. In the case of ultrasound, the straightness is very excellent and thus, a surveillance area is very narrow. In the case of IR, there are some constraints on a distance and a range capable of detecting thermal change. A camera may not detect an intrusion situation occurring in a dead zone such as a side, rear, and the like deviated from a general angle of view of the camera. A technology of detecting a sound of an intruder has a difficulty in detecting an intruder who does not make a sound, and frequently malfunctions due to peripheral noise. As a technology of generating and measuring a sound, a conventional technology of measuring a sound field variation determines that even a simple sound field variation is an intrusion and thus, there may occur a malfunction to determine that even a sound field variation occurring due to an environmental change by a change in temperature of air and the like is an intrusion.